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The cooling system for a nuclear reactor at Japan's Fukushima Daiichi plant lost power for hours Friday afternoon but was operational again, officials at the Tokyo Electric Power Company said.

The outage is one of several that has hampered the facility recently. There have been many repairs at the plant since the devastating earthquake and tsunami in March 2011 that triggered a nuclear disaster there.

Last month, power outages at the critical nuclear facility were blamed on rats short circuiting a switchboard, Japan's Kyodo news agency reported. Officials said at that time that the temporary power loss did not trigger a known release of radioactive material.

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The tsunami that hit Fukushima Daiichi after Japan's historic earthquake knocked out power and coolant systems at the plant, resulting in meltdowns in three reactors. The result was the worst nuclear accident since Chernobyl, as the crippled reactors spewed enormous amounts of radioactive particles into the environment.

The Tokyo Electric Power Company, the operator of the Fukushima plant, has said it is monitoring radiation contamination levels around the plant.